Abstract
Abstract. Land surface hydrology is an important control of surface weather and climate. A valuable technique to investigate this link is the prescription of soil moisture in land surface models, which leads to a decoupling of the atmosphere and land processes. Diverse approaches to prescribe soil moisture, as well as different prescribed soil moisture conditions have been used in previous studies. Here, we compare and assess four methodologies to prescribe soil moisture and investigate the impact of two different estimates of the climatological seasonal cycle used to prescribe soil moisture. Our analysis shows that, though in appearance similar, the different approaches require substantially different long-term moisture inputs and lead to different temperature signals. The smallest influence on temperature and the water balance is found when prescribing the median seasonal cycle of deep soil liquid water, whereas the strongest signal is found when prescribing soil liquid and soil ice using the mean seasonal cycle. These results indicate that induced net water-balance perturbations in experiments investigating soil moisture–climate coupling are important contributors to the climate response, in addition to the intended impact of the decoupling. These results help to guide the set-up of future experiments prescribing soil moisture, as for instance planned within the Land Surface, Snow and Soil Moisture Model Intercomparison Project (LS3MIP).
Highlights
The interplay between the land surface and the atmosphere can induce or modulate anomalies in temperature (Hirschi et al, 2011; Whan et al, 2015) and precipitation (e.g. Guillod et al, 2015)
Soil moisture is commonly prescribed in general circulation models to study the interplay of the land surface with weather and climate
As other types of sensitivity experiments, this approach introduces perturbations, in particular to the land water balance, because it artificially removes rainwater that infiltrates the soil and replaces water in the soil that is lost via evapotranspiration and drainage
Summary
The interplay between the land surface and the atmosphere can induce or modulate anomalies in temperature (Hirschi et al, 2011; Whan et al, 2015) and precipitation (e.g. Guillod et al, 2015). The interplay between the land surface and the atmosphere can induce or modulate anomalies in temperature (Hirschi et al, 2011; Whan et al, 2015) and precipitation The complex role of SM in land–atmosphere dynamics can be investigated with general circulation models (GCMs). In this context, land state variables are set – prescribed – to predefined target values in GCM simulations. Land state variables are set – prescribed – to predefined target values in GCM simulations Such experiments have been performed for decades Prescribing land state variables suppresses interactions between the land and the atmosphere and can be used to infer the role of land–atmosphere interactions for the climate
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